1. Field of the Invention
The present invention relates to a paper eject passageway auto-switching device, in particular to a device capable of automatically performing the selection of paper eject passageway without any switching unit installed therein.
2. Description of Prior Art
Scanners, facsimile machines, and printers are provided with paper feeders which are used to feed sheet papers into and to eject them out of the machines. The following is an explanation of the operation of a paper feeder installed in a sheet-feed type scanner. Documents to be scanned may be of different natures and different sizes. For example, a business card is quite different from an ordinary copy paper in bending resistance and size. FIGS. 1 and 2 are schematic drawings showing the operation of a conventional switching unit installed in a scanner. As shown in FIGS. 1 and 2, when a sheet paper is moving along a paper eject passageway, it can be ejected out of the scanner through an "A" passageway (see FIG. 1) or a "B" passageway (see FIG. 2). The switching between "A" passageway and "B" passageway is performed by a guide plate 30 which can be manually shifted between two locations respectively shown in FIG. 1 and FIG. 2. Namely, when the guide plate 30 is at the location shown in FIG. 1, the sheet paper is guided to pass around a feed roller 32. When the guide plate 30 is shifted upward to the location shown in FIG. 2, the sheet paper passes by the feed roller 32 and is expelled in a direction contrary to that shown in FIG. 1. However, if the guide plate 30 is at the location shown in FIG. 1, a business card is apt to become jammed between the feed roller 32 and the guide plate 30 due to its much greaten resistance to bending. Thus, when a business card is being scanned, the guide plate 30 has to be shifted upward to avoid jamming of the paper.